Magnetic random access memory and initializing method for the same

Abstract

A domain wall motion type MRAM has: a magnetic recording layer 10 having perpendicular magnetic anisotropy; and a pair of terminals 51 and 52 used for supplying a current to the magnetic recording layer 10 . The magnetic recording layer 10 has: a first magnetization region 11 connected to one of the pair of terminals; a second magnetization region 12 connected to the other of the pair of terminals; and a magnetization switching region 13 connecting between the first magnetization region 11 and the second magnetization region 12 and having reversible magnetization. A first pinning site PS 1 , by which the domain wall is trapped, is formed at a boundary between the first magnetization region 11 and the magnetization switching region 13 . A second pinning site PS 2 , by which the domain wall is trapped, is formed at a boundary between the second magnetization region 12 and the magnetization switching region 13 . A third pinning site PS 3 , by which the domain wall is trapped, is formed within the first magnetization region 11.

1. A magnetic random access memory of domain wall motion type comprising:
 a magnetic recording layer being a ferromagnetic layer having perpendicular magnetic anisotropy in which a domain wall moves; and 
 a pair of terminals used for supplying a current to said magnetic recording layer, 
 wherein said magnetic recording layer comprises: 
 a first magnetization region connected to one of said pair of terminals; 
 a second magnetization region connected to the other of said pair of terminals; and 
 a magnetization switching region connecting between said first magnetization region and said second magnetization region and having reversible magnetization, 
 wherein a first pinning site, by which the domain wall is trapped, is formed at a boundary between said first magnetization region and said magnetization switching region, 
 a second pinning site, by which the domain wall is trapped, is formed at a boundary between said second magnetization region and said magnetization switching region, and 
 a third pinning site, by which the domain wall is trapped, is formed within said first magnetization region. 
 
     
     
       2. The magnetic random access memory according to  claim 1 ,
 wherein said magnetic recording layer is formed such that the domain wall is trapped more stably by said third pinning site than by said first pinning site and said second pinning site. 
 
     
     
       3. The magnetic random access memory according to  claim 1 ,
 wherein said first magnetization region comprises: 
 a first region; and 
 a second region sandwiched between said first region and said magnetization switching region, 
 wherein said third pinning site is formed at a boundary between said first region and said second region. 
 
     
     
       4. The magnetic random access memory according to  claim 3 ,
 wherein a width of said magnetic recording layer at the boundary between said first region and said second region is larger on a side of said first region than on a side of said second region. 
 
     
     
       5. The magnetic random access memory according to  claim 4 ,
 wherein a constricted section is so formed in said second region as to be adjacent to the boundary between said first region and said second region. 
 
     
     
       6. The magnetic random access memory according to  claim 3 ,
 wherein a width of said first region becomes larger as away from the boundary between said first region and said second region towards inside of said first region. 
 
     
     
       7. The magnetic random access memory according to  claim 3 , further comprising: a magnetic layer formed on said first region. 
     
     
       8. The magnetic random access memory according to  claim 3 ,
 wherein said pair of terminals is connected to said second region and said second magnetization region, respectively. 
 
     
     
       9. The magnetic random access memory according to  claim 3 ,
 wherein a width of said magnetic recording layer at a boundary between said second region and said magnetization switching region is larger on a side of said second region than on a side of said magnetization switching region, and 
 a width of said magnetic recording layer at the boundary between said second magnetization region and said magnetization switching region is larger on a side of said second magnetization region than on a side of said magnetization switching region. 
 
     
     
       10. The magnetic random access memory according to  claim 3 ,
 wherein magnetic fields required for depinning the domain wall at said first pinning site towards said magnetization switching region and said first magnetization region are Hr1 and Hp1, respectively, 
 magnetic fields required for depinning the domain wall at said second pinning site towards said magnetization switching region and said second magnetization region are Hr2 and Hp2, respectively, and 
 magnetic fields required for depinning the domain wall at said third pinning site towards said first region and said second region are H1 and H2, respectively, and 
 wherein the following relational expressions are satisfied:
   Hp1<H1; 
   Hp2<H1; and 
   Hr1<H2<Hp2. 
 
 
     
     
       11. The magnetic random access memory according to  claim 1 ,
 wherein at a time of an actual operation, a magnetization direction of said first magnetization region is fixed in a first direction, and a magnetization direction of said second magnetization region is fixed in a second direction opposite to said first direction. 
 
     
     
       12. The magnetic random access memory according to  claim 11 , further comprising: a pinned layer being a ferromagnetic layer having perpendicular magnetic anisotropy and whose magnetization direction is fixed,
 wherein said pinned layer is connected to said magnetization switching region through a non-magnetic layer. 
 
     
     
       13. The magnetic random access memory according to  claim 11 , further comprising:
 a sense layer being a ferromagnetic layer magnetically coupled to said magnetization switching region and having reversible magnetization; and 
 a pinned layer being a ferromagnetic layer connected to said sense layer through a non-magnetic layer and whose magnetization direction is fixed.